Quantization is generally part of the functionality of an ADC, and most quantizers used in ADCs are linear. For example, many flash ADCs employs a resistor divider that divides a supply voltage evenly to generate several reference voltages that are equidistantly spaced apart. However, there are some conventional ADCs which have quantizers that are non-uniform, such as the ADC 100. As shown, ADC 100 generally comprises a sample-and-hold (S/H) circuit 102 and a non-uniform quantizer 104 (which includes a divider having resistors R1 to R8 and comparators 106-1 to 106-7). The resistors R1 to R8 have differing resistances (i.e., R to 5*R) so that the reference voltages applied to comparators 106-1 to 106-7 are non-uniformly spaced. These conventional ADCs, however, have many issues (i.e., high power consumption, low accuracy, etc.). Therefore, there is a need for an improved ADC architecture that employs non-uniform quantization.
Some other conventional circuits are: U.S. Pat. Nos. 5,801,657; 6,271,782; 7,859,441; Narayanasami et al. “A Design Technique for Nonuniform Quantizer in PCM Generation” IEEE Transactions on Circuits and Systems, Vol. CAS-29, Vol. 3, March 1982; Li et al., “A Second Order Sigma Delta Modulator Using Semi-uniform Quantizer with 81 dB Dynamic Range at 32×OSR,” Proc. Europrean Solide States Circuits Conference, pp. 579-582, September 2002; Syed Murtuza, “Non-Uniform Error-Sampled Control Systems,” Proc. of the 29th Conf. on Decision and Control, December 1990; and Bingxin Li, “Design of Multi-bit Sigma-Delta Modulators for Digital Wireless Communications,” Ph.D Dissertation, 2003.